1. Technical Field
This application relates in general to wireless communication systems, and more particularly to an improved system and method of updating e-mail messages between a mail server and a mobile communication device or between multiple external mailboxes and main mailbox, using mailbox pooling pre-emptive criteria
2. Description of the Related Art
It is known in the art to provide email polling of a central mail server for updating messages between remote users and. For example, Novell® provides a NetMail XE solution whereby a mail server installed at a branch/remote office receives e-mail messages from an Internet Service Provider (ISP), and distributes the received messages to users at the branch/remote office over a local area network. A mail sub-domain at the ISP forwards all e-mail for the remote office to the mail server, which functions as a mail cache, sending e-mail to and receiving e-mail from the ISP.
In the above-described system, the mail sub-domain at the ISP is polled by the mail server to send or receive messages, regardless of whether the mailbox has any new incoming or outgoing messages. In large systems, this polling method may consume large amounts of server resources and impact performance. The consumption of resources and performance impact is more pronounced when mailbox polling occurs on mobile devices over bandwidth-limited wireless networks. For example, if a mail server with 1000 mailboxes is polled and sends updates every 15 minutes to 1000 mail applications running on wireless devices, the wireless network will become severely congested resulting in significant service delays.
In order to address this shortcoming, a new polling method has been proposed for use with mobile communication devices, such as wireless data communicators. This new polling method, referred to as ‘adaptive polling’ provides mailbox updates based on a trigger event. Adaptive polling automatically determines the polling interval of the user based on his usage profile. A description of adaptive polling is set forth in U.S. Patent Application No. 60/493,118 filed Aug. 7, 2003, the contents of which are incorporated by reference. In this system, a remote wireless subscriber can integrate external mailboxes (e.g. POP accounts) to his/her mobile wireless account via a POP polling engine that periodically polls new e-mails from the external accounts and places new e-mails into the user's mobile wireless account mailbox to be delivered to his/her mobile communication devices. When the polling engine polls an external mailbox, it requests the current list of message IDs from the external mailbox and checks each entry in the list to see if it has already been stored in a local database. If the message ID is not found in the database, it is deemed to be a new e-mail and will be retrieved. Once the new e-mail has been retrieved, the message ID is added to the database so as to prevent subsequent re-retrieval during subsequent polls. If the message ID is found in the database, it is deemed to be an old message and is ignored. The adaptive algorithm varies the polling frequency based on the volume of e-mail traffic that the user is experiencing. However, for each external POP account, the polling engine has to be able to determine if the external account has new e-mails, and which ones are new.
The adaptive polling technique set forth above suffers from performance problems in that every message ID must be checked against the database for every poll. Accordingly, the technique is not efficient for large mailboxes and large numbers of mailboxes.
In the present specification, the term “polling” is used to indicate detecting new messages, retrieving detected new messages and sending the messages to a device or mailbox. Thus, polling differs from synchronization, by which messages on a user device/main mailbox are completely synchronized with messages in the user's mailbox/multiple external mailboxes. Whereas polling may occur with relatively high frequency, full synchronization is performed periodically (at a time interval that is much longer than the polling interval), or in response to a user request via his/her device for full synchronization.